One of the common problems in connection with the use of solid waste materials such as municipal refuse for use in producing heat or electricity is providing a uniform supply of the appropriate amount of fuel to the furnace. Municipal waste contains a variety of different types of combustible materials including paper, plastic, leather and fabric. In common prior art systems these materials are fed to shredding apparatus and comminuted to form small pieces of material which can then be fed to the furnace by a conveying means. It is also common that the waste material is not thoroughly shredded and may include lengths of fabric, rope, twine or wire.
In one conventional apparatus for use in feeding refuse material to a furnace, comminuted or shredded refuse material is housed in a large bin and a plurality of augers are housed in the bottom of the bin. The augers feed refuse material to a plurality of fuel charging devices, and the fuel charging devices in turn feed the waste material to the furnace. During the operation of these machines, wire, rope twine or other lengths of material may become wound around the augers at the bottom of the large bin placing a heavy load on the auger drive system or stopping the augers entirely. Waste material can also become jammed in the auger flights or between the auger flights and the auger housing. It is common that the waste material may be 15 or 20 feed deep in the bin, and servicing of the augers requires removal of the material above the augers.
Another problem encountered with augers for use in feeding waste material to a furnace is that hard materials may become jammed between the peripheral edges of the auger flights and the inside surface of the auger trough or housing thereby causing the auger to stop. In many common auger arrangements, the periphery of the auger is closely spaced with respect to the inner surface of an auger trough. Pieces of metal, stones or cinders in the refuse can be wedged between the auger flight and the housing, thereby stopping the auger.
One of the requirements of a fuel delivery system for commercially successful boilers is that fuel may be delivered at a uniform rate for extended periods of time. Interruptions in the delivery of fuel to the boiler are undesireable, and auger constructions are not commercially functional if the auger can be stopped by accumulations of materials or lengths of materials becoming wound around the auger or as a result of hard materials becoming jammed between the auger flight and the auger trough.